Office chair keeps sinking

What's actually wrong

The pneumatic gas cylinder has lost its seal and can no longer hold pressure. This is the single most common office chair failure — and one of the cheapest, easiest fixes in the entire office.

Symptoms

• Chair slowly sinks while you sit
• Height lever does nothing
• Chair won't stay at set height

The fix, step by step

1. Confirm it's the cylinder: if the chair sinks under weight but rises when empty, the cylinder is done
2. Order a universal replacement gas cylinder — office chair cylinders are standardized (universal fit covers the vast majority of chairs); heavy-duty versions exist for 300+ lb ratings
3. Remove the old cylinder: flip the chair, tap the mechanism plate off the cylinder taper with a mallet, then use a pipe wrench to twist the cylinder out of the base
4. Drop the new cylinder into the base, set the seat mechanism onto it, and sit — your weight seats the taper
5. Total time: about 15 minutes. The 'clamp/hose-clamp on the piston' hack works as a temporary lock at one height, but a $25–40 cylinder is the real fix

When to skip DIY

Almost never — this is the definitive DIY office repair. For premium chairs under warranty, use the warranty instead: Herman Miller's 12-year warranty covers pneumatic cylinders, and Steelcase covers cylinders and mechanisms for 12 years (its 'lifetime' coverage applies to the frame). One caveat: some Herman Miller/Steelcase and heavy-duty chairs use non-standard cylinders — check before ordering a universal one.